Coal is a kind of complex porous medium, in pore structure of which a lot of methane and carbon dioxide gas are absorbed. As the exploration of coal resource is performed towards deep coal seam, low-gas mine gradually turns into high-gas mine, and the absorbed gas is desorbed to be in free-state with the increment of environment temperature and the decrement of stress, and migrates in the pore structure of the coal. During the exploration and excavation in deep coal-rock mass, although the free-state gas may go out of roadways upon the ventilation of the mine, much gas is still absorbed in the coal-rock mass, which becomes one factor that causes various gas accidents. As a result, research on desorption and migration characteristics of the absorbed gas occurring in the coal seam is a technical difficulty in the mining safety engineering, and is also an urgent problem that needs to be solved.
Currently, the vast majority of researches on the desorption-migration process of the gas absorbed in the coal-rock mass focus on the amount of absorbed gas and desorbed gas in different temperature and pressure conditions, whereby the absorbing-desorbing ability of the tested coal sample is evaluated. The process of the conventional research will be described below: first, performing a vacuum degassing to the collected coal sample; then injecting air with a certain pressure to make the coal sample achieve absorption saturation; thereafter, performing a pressure relief and desorption process, and detecting the desorbed gas with instruments such as a flow meter, a pressure meter or the like to accomplish the experiment process. In the above-mentioned process, although a maximum adsorption gas amount of the coal sample and the Langmuir adsorption constant under isothermal condition can be obtained, it cannot reflect migration regulation of the gas absorbed in the coal seam in multiple physical fields, such as a temperature field, a stress field and a seepage field, before and after the exploration, and also cannot realistically simulate the absorbing-desorbing process of the gas in the coal-rock mass under real environment in deed. As a result, experiment data will be lack of reliability to some extent, such that it fails to provide a basis for accurately determining the forming time and reason of gas outburst, and may generate a potential danger for safety production.